Field of the Invention
This invention is the exogenous application of serotonin, melatonin and related derivatives to regulate flowering in plants. Flowering involves the developmental transition of the shoot meristem from vegetative to reproductive growth. In the majority of species of flowering plants, which includes nearly all crop plants and horticultural species, the transition to flowering is regulated by daylength, and thus these species are considered to be "photoperiodic" with regard to their reproductive regulation. This limits year-round production of many crops, and breeding efforts to modify photoperiodic behavior have been critical to development of early season varieties in crops such as strawberry.
Melatonin is known to be a potent hormone associated with photoperiodic reproductive behavior in animals, lower organisms and dinoflagellates and its cell and molecular biology has been extensively investigated in animal systems. However, melatonin has not been previously reported in plants. This invention is based on the discovery that melatonin induces flowering in plants. The metabolic pathway for production of melatonin uses serotonin as a precursor (see FIG. 1). The relative amounts of serotonin to melatonin are responsible for triggering flowering. Exogonous levels of serotonin are able to inhibit flowering.
Regulation of flowering is of significant economic value. The inhibition of premature flowering and stimulation of flowering after a plant reaches maximal size can increase flower and seed yields dramatically. Alternatively, in geographical regions where the growing season is short, the stimulation of precocious flowering can increase the range of late-maturing crops, for example soybean. Finally, by stimulating flowering to be uniform among a field or stand, harvest costs can be minimized.